IgG isotypic antibodies to crude Plasmodium falciparum blood-stage antigen  associated with placental malaria infection in parturient Cameroonian women.

Judith K Anchang-Kimbi, Eric Akum Achidi, Blaise Nkegoum, Joseph-Marie N Mendimi, Eva Sverremark-Ekström, Marita Troye-Blomberg
1. Department of Zoology and Animal Physiology, University of Buea, Buea 63.
2. Department of Biochemistry and Molecular Biology , University of Buea, Buea-63, Cameroon.
3. Department of Anatomy and Pathology, University of Yaoundé Teaching Hospital, Yaoundé-812.
4. Department of Anatomy and Pathology, University of Yaoundé I Teaching Hospital, Yaoundé-812.
5. Department of Molecular Bioscience, Wenner-Gren Institute, Stockholm University, SE-10691 Stockholm.
6. Department of Molecular Bioscience, Wenner-Gren Institute, Stockholm University, SE- 10691 Stockholm.

Abstract
Background: Few studies have reported an association between placental malaria (PM) infection and levels of isotypic antibodies against non-pregnancy associated antigens.

Objective: To determine and evaluate IgG isotypic antibody levels to crude P. falciparum blood stage in women with and without PM infection.

Methods:Levels of IgG (IgG1-IgG4) and IgM to crude P. falciparum blood stage antigen were measured by ELISA in 271  parturient women. Placental malaria infection was determined by placental blood microscopy and placental histology. Age, parity  and intermittent preventive treatment during pregnancy with sulphadoxine-pyrimethamine (IPTp-SP) usage were considered  during analysis.

Results: P. falciparum-specific IgG1 (96.5%) and IgG3 (96.7%) antibodies were predominant compared with IgG2 (64.6%) and
IgG4 (49.1%). Active PM infection was associated with significant increased levels of IgG1, IgG4 and IgM while lower levels  of these antibodies were associated with uptake of two or more IPTp-SP doses. PM infection was the only independent factor  associated with IgG4 levels. Mean IgG1 + IgG3/IgG2 + IgG4 and IgG1 + IgG2 +IgG3/ IgG4 ratios were higher among the PM-uninfected group while IgG4/IgG2 ratio prevailed in the infected group.

Conclusion:PM infection and IPTp-SP dosage influenced P. falciparum-specific isotypic antibody responses to blood stage  antigens. An increase in IgG4 levels in response to PM infection is of particular interest.

Keywords: Placental malaria infection, isotypic antibodies, crude Plasmodium falciparum antigen